[2369] Add InputSource helper class (work-in-progress)

src/lib/dns/inputsource.cc

@@ -0,0 +1,74 @@
+// Copyright (C) 2012  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+#include <dns/inputsource.h>
+#include <exceptions/exceptions.h>
+
+namespace isc {
+namespace dns {
+namespace master_lexer_internal {
+
+int
+InputSource::getChar() {
+    if (buffer_pos_ == buffer_.size()) {
+        // We may have reached EOF at the last call to
+        // getChar(). at_eof_ will be set then. We then simply return
+        // early.
+        if (at_eof_) {
+            return -1;
+        }
+        // We are not yet at EOF. Read from the stream.
+        int c = input_.get();
+        // Have we reached EOF now? If so, set at_eof_ and return early,
+        // but don't modify buffer_pos_ (which should still be equal to
+        // the size of buffer_).
+        if (!input_.good()) {
+            at_eof_ = true;
+            return -1;
+        }
+        buffer_.push_back(c);
+    }
+
+    int c = buffer_[buffer_pos_++];
+    if (c == '\n') {
+        line_++;
+    }
+
+    return (c);
+}
+
+void
+InputSource::ungetChar() {
+    if (at_eof_) {
+        at_eof_ = false;
+    } else if (buffer_pos_ == 0) {
+        isc_throw(OutOfRange, "Cannot skip before the start of buffer");
+    } else {
+        if (buffer_[buffer_pos_] == '\n') {
+            line_--;
+        }
+        buffer_pos_--;
+    }
+}
+
+void
+InputSource::ungetAll() {
+    buffer_pos_ = 0;
+    line_ = saved_line_;
+    at_eof_ = false;
+}
+
+} // namespace master_lexer_internal
+} // namespace dns
+} // namespace isc